Energy flux determines magnetic field strength of planets and stars
Energy flux determines magnetic field strength of planets and stars
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DOI：
10.1038/nature07626
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发表时间：
2009-01-08
期刊：
影响因子：
64.8
通讯作者：
Reiners, Ansgar
中科院分区：
文献类型：
--
作者：
Christensen, Ulrich R.;Holzwarth, Volkmar;Reiners, Ansgar
地球和木星的磁场，以及沿着快速旋转的低质量恒星的磁场，都是由对流驱动的发电机产生的，这些发电机的运行方式可能类似（1-4）（缓慢旋转的太阳通过不同的发电机机制产生磁场（5））。行星和恒星的磁场强度变化超过三个数量级，但导致这种变化的关键因素迄今尚不清楚（5，6）。在这里，我们报告了一个扩展的标度律来自地球发电机模型（7）的快速旋转的恒星，有很强的密度分层。标度律的统一原理是，可用于产生磁场的能通量决定了磁场强度。我们的标度定律符合地球，木星，年轻的收缩恒星和快速旋转的低质量恒星的观测场强，尽管物体的物理条件存在巨大差异。我们预测，快速旋转的褐矮星和大质量太阳系外行星的场强足够高，可以观测到它们。
Themagnetic fields of Earth and Jupiter, along with those of rapidly rotating, low- mass stars, are generated by convection- driven dynamos that may operate similarly(1-4) ( the slowly rotating Sun generates its field through a different dynamo mechanism(5)). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear(5,6). Here we report an extension of a scaling law derived from geodynamo models(7) to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.